[bluevp00]

What you are describing is commonly referred to as a "mini-me" swap; that is, putting a VTEC cylinder head on a non-VTEC car.

To answer some of your questions: Yes, the EX and DX use the exact same engine block, the only part that you will have to swap is the cylinder head. The EX cylinder head is an exact fit onto the DX block, no fabrication is necessary.

Yes, you will need to make alterations to your car's computer, but you don't need a completely new computer. A "VTEC controller" is what you'll need in order for VTEC to work.

There's a lot of info in this forum on this type of head swap, just type in "mini me" or "head swap" into the search box.